Sulfamate-carboxylate derivatives are useful compounds as synthetic materials or intermediates for medicine. For example, they can be used as a synthetic intermediate of a compound having NPYY5 receptor antagonistic activity described in Patent Document 1.
Patent Document 1 discloses a process for the preparation of 4-(2-methylpropane-2-sulfonylamino-1-cyclohexanecarboxylic acid comprising subjecting 4-amino-1-cyclohexanecarboxylic acid methyl ester and t-butylsulphinyl chloride to the coupling reaction in a dichloromethane solvent, oxidizing the obtained compound, and then hydrolyzing. It is difficult to use industrially this process, because it is necessary that restricted-use dichloromethane is used and the product is isolated by chromatography.
Patent Document 2 discloses a process for the preparation of trans-4-(2-methylpropane-2-sulfonylamino-1-cyclohexanecarboxylic acid comprising subjecting cis-4-amino-1-cyclohexanecarboxylic acid methyl ester and t-butylsulphinyl chloride to the coupling reaction in an ethyl acetate solvent, the oxidation reaction, transformation to trans isomer, and then hydrolysis. This process was far from a high-yielding preparation process as the yield from cis-4-amino-1-cyclohexanecarboxylic acid to trans-4-(2-methylpropane-2-sulfonylamino)cyclohexanecarboxylic acid is 70% or less even if the loss in transformation to trans isomer was excluded.
Additionally, the document discloses an example that tetrahydrofuran is used in a coupling step. However, the process was needed to improve as a process for the industrial preparation, because it was necessary to isolate the reaction intermediates in every step, operations were complicated and the preparation efficiency was not high.    [Patent Document 1] WO01/37826    [Patent Document 2] WO2003/076374